1. Field
This invention relates to germicidal compositions generally, and to an anionic detergent and iodine commposition specifically.
2. State of the Art
For purposes of this disclosure, a disinfectant is a chemical applied to inanimate surfaces for the purpose of destroying microorganisms. An antiseptic is a chemical applied to living tissue for the purpose of preventing or arresting the growth of microscopic pathogens. Germicides incorporate the properties of both disinfectants and antiseptics.
Iodine's use in medicine dates back to at least 1830 when it was used as an antiseptic to treat wounds. Today, iodine is still recognized as a good general purpose antiseptic provided that appropriate dilutions of the compound are used. In addition, iodine is the active ingredient in numerous disinfectants.
Three classical iodine-containing formulations are Iodine Solution (USP), Strong Iodine Solution (USP), and Iodine Tincture (USP). Iodine Solution (USP) is understood to contain 1.8 to 2.2 grams (g) of iodine and 2.1 to 2.6 g of sodium iodide (NaI) in each 100 milliliters (ml) of water. Strong Iodine Solution (USP) (e.g. Lugol's Solution), contains 4.5 to 5.5g of iodine, and 9.5 to 10.5 g of potassium iodide (KI) in each 100 ml of water. Iodine Tincture (USP) preparations typically contain 1.8 to 2.2 g of iodine, and 2.1 to 2.6 g of NaI in a 100 ml solution of water and alcohol (50% by volume). All three of these preparations are effective as antiseptics, but are also highly toxic and bad smelling.
Iodine, although a good antiseptic, does have some drawbacks in high concentrations. It smells unpleasant, stains the skin a yellowish-brown, stains starch-containing materials blue, is unstable in solution, and can irritate or burn animal tissue.
As a disinfectant, iodine by itself has a limited ability to kill spores and may react chemically with metals and other materials, causing erosion.
To overcome some of the drawbacks associated with the use of iodine solutions as antiseptics, the iodophors were developed. Iodophors are generally defined as complexes of iodine and nonionic or cationic detergents which release iodine in water. Typical detergents used in compounding antiseptic iodophors are polyvinyl pyrrolidone, polyether glycols, polyvinyl alcohols, polyacrylic acids, polyamides, and polyoxy alkylenes.
Exemplary of the antiseptic iodophors is "PVP-iodine" or "povidone iodine" (Betadine.RTM. by Purdue-Frederick). Povidone iodine contains polymeric polyvinyl pyrrolidone. When povidone iodine is diluted with water, free iodine releases into the solute.
Povidone iodine, like the other iodophors, has the unusual characteristic of having a specific dilution ratio (the "use-dilution") at which a maximum concentration of free iodine will be present in solution. "Free iodine," as used in this disclosure, is the concentration of the nonionic, antimicrobial species I.sub.2 and HOI. L. Gershenfeld, et al., Iodine as An Antiseptic, Annals New York Academy of Sciences, 53:172-182 (1950). Mixing an iodophor with less water than that used with the use-dilution results in a decreased concentration of free iodine. Povidone iodine has a maximum attainable free iodine concentration of 25.6 ppm, which concentration is attainable at povidone iodine's use-dilution. S. Block, Disinfection, Sterilization, and Preservation, 183-196, 1983.
"Use-dilution" is not to be confused with "dilution of use." Dilution of use, as used in this disclosure, means the dilution or concentration at which the particular germicidal composition is used for whatever reason. The dilution of use need not necessarily be the dilution at which the maximal concentration of free iodine would be present.
The iodophors are benign to living tissue and lack the pungent odor characteristic of iodine containing solutions. These characteristics of the iodophors render them preferable to strong solutions of iodine (e.g., the three aforementioned USP preparations). R. Blatt et al., An Evaluation of the Iodophor Compounds as Surgical Germicides, J. Surgery, Gynecology and Obstetrics, 113:699-704 (1961).
The advantages gained by using the iodophors are offset to some extent by some disadvantages. Since each iodophor has a self-limiting maximum concentration of free iodine, and free iodine is the active germicidal agent, L. Gershenfeld, et al., Iodine as An Antiseptic, Annals New York Academy of Sciences, 53:172-182 (1950), more time is required for the iodophors to disinfect a treated area when compared with the aforementioned iodine solutions. For example, Wescodyne.RTM., a well known disinfectant, has a maximum free iodine concentration of 20 milligrams/liter (mg/l) at its use-dilution and requires a contact time of ten minutes to fulfill the criteria of an intermediate-level disinfectant (Environmental Protection Agency/Center for Disease Control standards).
A ten minute contact time can be excessive for busy medical or dental practices. Conditions in medical and dental offices, as well as emergency rooms, require successive patients to be treated at the same work station. The work station must be disinfected between each patient. Preoperative and postoperative disinfection are other common uses of the iodophors where a decreased treatment time would be useful.
Work has been done using undecoylium chloride-iodine, a complex of acycloaminoformylmethylpyridinium chloride and iodine. Undecoylium chloride-iodine has the activity of a cationic detergent and iodine's disinfectant action. This agent also has uses in preoperative and postoperative disinfection.